The Linux kernel, foundational for servers, desktops, embedded systems, and cloud infrastructure, has been under heightened scrutiny. Several vulnerabilities have been exploited in real-world attacks, targeting critical subsystems and isolation layers. In this article, we’ll walk through major examples, explain their significance, and offer actionable guidance for defenders.

CVE-2025-21756 – Use-After-Free in the vsock Subsystem

One of the most alarming flaws this year involves a use-after-free vulnerability in the Linux kernel’s vsock implementation (Virtual Socket), which enables communication between virtual machines and their hosts.

How the exploit works: A malicious actor inside a VM (or other privileged context) manipulates reference counters when a vsock transport is reassigned. The code ends up freeing a socket object while it’s still in use, enabling memory corruption and potentially root-level access.

Why it matters: Since vsock is used for VM-to-host and inter-VM communication, this flaw breaks a key isolation barrier. In multi-tenant cloud environments or container hosts that expose vsock endpoints, the impact can be severe.

Mitigation: Kernel maintainers have released patches. If your systems run hosts, hypervisors, or other environments where vsock is present, make sure the kernel is updated and virtualization subsystems are patched.

CVE-2025-38236 – Out-of-Bounds / Sandbox Escape via UNIX Domain Sockets

Another high-impact vulnerability involves the UNIX domain socket interface and the MSG_OOB flag. The bug was publicly detailed in August 2025 and is already in active discussion.

Attack scenario: A process running inside a sandbox (for example a browser renderer) can exploit MSG_OOB operations on a UNIX domain socket to trigger a use-after-free or out-of-bounds read/write. That allows leaking kernel pointers or memory and then chaining to full kernel privilege escalation.

Why it matters: This vulnerability is especially dangerous because it bridges from a low-privilege sandboxed process to kernel-level compromise. Many systems assume sandboxed code is safe; this attack undermines that assumption.

Mitigation: Distributions and vendors (like browser teams) have disabled or restricted MSG_OOB usage for sandboxed contexts. Kernel patches are available. Systems that run browser sandboxes or other sandboxed processes need to apply these updates immediately.

CVE-2025-38352 – TOCTOU Race Condition in POSIX CPU Timers

In September 2025, the U.S. Cybersecurity & Infrastructure Security Agency (CISA) added this vulnerability to its Known Exploited Vulnerabilities (KEV) catalog.